Structure for Cooling Heat Generator and Power Conversion Equipment

ABSTRACT

The disclosed invention provides power conversion equipment in which the thermal resistance of thermal connections is reduced. A structure for cooling a heat generator includes a heat generator having at least one cooled surface having protruding convex portions formed thereon, a heat receiving spacer in which hollow portions into which the convex portions are inserted are formed, clamping members which press and clamp the heat receiving space and the heat generator sandwiched therebetween, and a cooler which cools the heat receiving spacer. In an engagement state in which the heat generator and the heat receiving spacer are engaged by the clamping members, a distance between the cooled surface and the end faces of the convex portions is smaller than a distance between the cooled surface and a face, facing either of the clamping members, of the heat receiving spacer.

BACKGROUND

The present invention relates to a structure for cooling a heat generator and power conversion equipment.

An Uninterruptible Power-supply System (hereinafter abbreviated to UPS) is equipment for stable supply of electric power to a load without interruption in case abnormal condition occurs with a utility power source or the like which is a steady power source. There is a high demand of UPS for application in, inter alia, data centers along with ongoing innovation of IT utilization. Because UPSs for data centers center are installed in urban neighborhood where land prices are high, reduction in installation area, in other words, equipment downsizing is hoped for.

To downsize an UPS, it is important to downsize the components of the UPS. Above all, power conversion equipment occupies a large physical volume and, therefore, its downsizing is significantly effective. To pursue downsizing of the power conversion equipment, what is required is downsizing of a mechanism for cooling a power semiconductor module which is a heat generator and a more efficient cooling method through that mechanism.

As a method for air-cooling a power semiconductor module, for example, in Japanese Unexamined Patent Application Publication No. 2000-269671, there is the following description. “A first heat sink 25 is mounted on a CPU 23 with the intermediate positioning of a heat transfer sheet 26. A plurality of heat transfer portions 25 a are formed on the first heat sink 25. A second heat sink 27 is placed on the first heat sink 25. On the second heat sink 27, openings 29 are formed such that the heat transfer portions 25 a can be inserted therein with a gap. The gaps between the heat transfer portions 25 a and the openings 29 are filled with heat conductive grease.”

SUMMARY

The air-cooling method described in Japanese Unexamined Patent Application Publication No. 2000-269671 enables expanding heat dissipation areas by the connections between the convex portions and the openings and reducing the thermal resistance of a heat conductive grease layer, while reducing the load applied to an electronic part. However, since heat that has once been conducted to a holding member is allowed to conduct up to the rear surface of a heat generating member and dissipated to a substrate, there is large thermal resistance in conduction, and heat dissipation performance is limited.

An object of the present invention is to provide power conversion equipment downsized by reducing the thermal resistance of thermal connections and improving heat dissipation performance.

In order to achieve the above object, a structure for cooling a heat generator is provided, including, for example, a heat generator having at least one cooled surface having protruding convex portions formed thereon, a heat receiving spacer in which hollow portions into which the convex portions are inserted are formed, clamping members which press and clamp the heat receiving space and the heat generator sandwiched therebetween, and a cooler which cools the heat receiving spacer. In an engagement state in which the heat generator and the heat receiving spacer are engaged by the clamping members, a distance between the cooled surface and the end faces of the convex portions is smaller than a distance between the cooled surface and a face, facing either of the clamping members, of the heat receiving spacer.

According to the present invention, the convex portions are connected to the cooler via a heat conductive material and, therefore, heat from a power semiconductor module can be transferred to the cooler efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of power conversion equipment pertaining to one embodiment of the present invention;

FIG. 2 is a circuit diagram of a converter in the power conversion equipment;

FIG. 3 is a circuit diagram of an inverter in the power conversion equipment;

FIG. 4 is a circuit diagram of a charging/discharging chopper in the power conversion equipment;

FIG. 5 is a circuit diagram of a dual-side cooled power module which is used in the present embodiment;

FIG. 6 is an external view of the dual-side cooled power module which is used in the present embodiment;

FIG. 7 is a perspective view of a heat receiving spacer;

FIG. 8 is a diagram depicting a state in which heat receiving spacers are attached to the dual-side cooled power module;

FIG. 9 is a cross-sectional view through line A-A′ in FIG. 8;

FIG. 10 is a perspective view depicting a state in which two dual-side cooled power modules are attached to a cooler;

FIG. 11 is an exploded view of region B surrounded by dashed lines presented in FIG. 10;

FIG. 12 is a cross-sectional view through line C-C′ in. FIG. 11;

FIG. 13 is an enlarged view of portion D presented in FIG. 12;

FIG. 14 depicts a second embodiment of the present invention, in which thermal connections in the first embodiment are provided by heat conductive sheets 451;

FIG. 15 is an enlarged view of portion E in FIG. 14;

FIG. 16 depicts a third embodiment of the present invention, in which the power semiconductor module of the first embodiment is configured as a one side cooled power module; and

FIG. 17 is an enlarged view of portion F in FIG. 16.

DETAILED DESCRIPTION

In the following, embodiments for carrying out the present invention will be described with reference to the drawings.

First Embodiment

FIG. 1 is a circuit diagram of power conversion, equipment 1 pertaining to one embodiment of the present invention.

This system assumed to operate as UPS is an uninterrupted inverter-fed power supply system which can continue to supply electric power without instantaneous interruption in case of electric power outage. Three-phase AC voltage from a utility power source 2 is supplied through a steady power source side switch 21 and a filtering circuit for input 17 for eliminating harmonics and to a converter 11 and converted from AC to DC by the converter 11 which is a rectification circuit. After rectification at the converter 11, a DC voltage 4 smoothed by a capacitor 20 is applied to an inverter 12 and inversely converted to AC of a desired voltage and frequency. After inverse conversion, three-phase AC voltage 5 which is output by the inverter 12, after its harmonic components are eliminated by a filtering circuit for output 18, is supplied via a load side switch 24 to a load 3. In the uninterrupted inverter-fed power supply system, the utility power source 2 of three-phase AC voltage constantly supplies power via the converter 11 and inverter 12 to the load 3. Therefore, in case a voltage fluctuation such as instantaneous voltage drop occurs with the utility power source 2, it is enabled to stably supply power that is equivalent to normal utility power by controlling the converter 11 and inverter 12. The operations of the converter 11 and inverter 12 and ON/OFF of the steady power source side switch 21 and the load side switch are controlled by a signal from a higher level control circuit 201.

In the meantime, a charging/discharging chopper 13 is connected to a stage preceding the inverter 12. When normal utility power is supplied, the charging/discharging chopper 13 operates as a step-down chopper which decreases the DC voltage 4 and outputs charging power 7 for charging a battery 14. A non-steady power source side switch 22 has a role to make connections to power feeding paths when feeding power from the battery 14 to the converter 11. A battery protecting switch 23 has a role to protect the battery from overcurrent or the like. The charging/discharging chopper 13, non-steady power source side switch 22, and battery protecting switch 23 are controlled by a signal from the higher level control circuit 201.

The converter 11, inverter 12, and charging/discharging chopper 13 generate heat during their operation and their temperature rises. To suppress this temperature rise, cooling wind 10 generated by a cooling fan 9 (air blower) is fed in to circulate and cool the inside of the power conversion equipment 1.

FIG. 2 is a circuit diagram of the converter 11 which is a component of the power conversion equipment 1.

The converter 11 converts a three-phase AC voltage from the utility power source 2 to a DC voltage 4. When normal utility power is supplied, incoming three-phase AC power is supplied to AC terminals 41 r, 41 s, 41 t of the converter 11 and rectified with switching elements 31 and rectification elements 33 in an upper arm and switching elements 32 and rectification elements 34 in a lower arm, these elements being provided for the respective phases. In the present embodiment, Insulated Gate Bipolar Transistors (IGBTs) are used as the switching elements and diodes are used as the rectification elements; however, these are non-limiting and other types of elements can also be applied (the same applies hereinafter). The switching elements 31, 32 of the converter 11 are driven by a signal from a control circuit 202.

FIG. 3 is a circuit diagram of the inverter 12 which is a component of the power conversion equipment 1.

The inverter 12 converts DC power smoothed by the capacitor which is not depicted to three-phase AC power. DC voltage produced by the converter 11 is converted to a three-phase AC voltage with switching elements 31 and rectification elements 33 in an upper arm and switching elements 32 and rectification elements 34 in a lower arm, these elements being provided for the respective phases, and the three-phase AC voltage is output to AC terminals 42 u, 42 v, 42 w. The switching elements 31, 32 of the inverter 12 are driven by a signal from a control circuit 203. The inverter 12 converts a DC voltage to an AC voltage regardless of condition of the utility power source 2 and outputs rated electric power to the filtering circuit for output 18.

FIG. 4 is a circuit diagram of the charging/discharging chopper 13 which is a component of the power conversion equipment 1.

The charging/discharging chopper 13 decrease the DC voltage and outputs charging power, when normal utility power is supplied by the utility power source 2. While switching elements 31 in an upper arm are ON, first, electromagnetic energy is accumulated in a reactor, which is not depicted, connected between the battery 14 and the charging/discharging chopper 13. Then, upon switching of the switching elements 31 in the upper arm to OFF, counter electromotive force is generated in the reactor and the electromagnetic energy in the reactor is discharged to charge the battery 14. On the other hand, when abnormal condition occurs with the utility power source, the charging/discharging chopper 13 converts a low DC voltage to a high DC voltage. First, electric power discharged by the battery 14 is supplied to the reactor and electromagnetic energy is accumulated in the reactor, while switching elements 32 in a lower arm are ON. Then, upon switching of the switching elements 32 in the lower arm to OFF, rectification elements 33 in the upper arm are turned ON by counter electromotive force of the reactor. Thereby, a voltage that is the sum of the DC voltage of the battery 14 and the counter electromotive voltage of the reactor appears at the output terminal of the charging/discharging chopper 13, which thus results in a voltage increase. The switching elements 31, 32 of the charging/discharging chopper 13 are driven by a signal from a control circuit 204. Although, in the present embodiment, there are two parallel legs in the charging/discharging chopper 13, the number of parallel legs is determined by the amount of electric power to be supplied to the charging/discharging chopper 13 when discharging takes place.

As will be noted from the foregoing, the converter 11, inverter 12, and charging/discharging chopper 13 which are installed in the power conversion equipment 1 of the present embodiment are basically configured with legs 35 in which the switching elements 31 and the rectification elements 33 are connected in series in the upper arm and the switching elements 32 and the rectification elements 34 are connected in series in the lower arm. In a case where electric power that is supplied to the load 3 exceeds rated power of the power conversion equipment 1, the rated power should be increased by increasing the number of parallel legs 35 in the converter 11, inverter 12, and charging/discharging chopper 13.

In the converter 11, inverter 12, and charging/discharging chopper 13, the resistors incorporated in the switching elements 31, 32 and the rectification elements 33, 34 give rise to loss, when these components carry current. Besides, switching from a current carrying state to a current blocking state gives rise to loss. Because heat is generated during operation entailing this loss, the temperature of the converter 11, inverter 12, and charging/discharging chopper 13 rises.

FIG. 5 is a circuit diagram of a dual-side cooled power module 100 which is used in the present embodiment. In the dual-side cooled power module 100, switching elements 31, 32 and rectification elements 33, 34 mounted on an insulator 112 are included. Respective semiconductors are interconnected to form a leg 35 which is depicted in FIGS. 2 to 4. Onto the insulator 112, a P terminal 113P (DC positive terminal), an N terminal 113N (DC negative terminal), an AC terminal. 113AC (AC terminal), and a gate terminal 111 for ON/OFF control of the switching elements are attached.

FIG. 6 is an external view of the dual-side cooled power module 100 which is used in the present embodiment. The dual-side cooled power module 100 is comprised of a substantially cuboidal main body part 101, a substantially cuboidal flange part 102 formed to expand one lateral side of the main body part 101, and a terminal block part 103 which is comprised of a plurality of terminals, protruding from a face of the flange part 102 on the side opposite to the main body part 101. Terminals constituting the terminal block part 103 are as follows: P terminal 113P, N terminal 113N, AC terminal 113AC, and gate terminal 111 depicted in FIG. 5.

One face 121A of the main body part 101 has a great number (e.g., a total of approx. 200 or more) of protruding pin fins 122A which are very small, columnar projections. On another face 121B of the main body part 101, opposite to the face 121A, as many pin fins 122B (not depicted) as the number of the pin fins 122A are also formed. Hereinafter, the pin fins 122A and 122B will be collectively termed “pin fins 122”. The pin fins 122 may be any convex portions formed to protrude from the faces 121A, 121B, besides the form of pin fins as depicted in this drawing. The main body part 101 has cooled surfaces 121A, 121B which are regions where the pin fins 122 are formed on the faces 121A, 121B. The cooled surfaces 121A and 121B are collectively termed “cooled surfaces”. The thickness of the main body part 101 with the exception of the pin fins 122, that is, the distance between the cooled surfaces 121, 121B is denoted by “d1”.

FIG. 7 is a perspective view of a heat receiving spacer. A pair of heat receiving spacers 300A, 300B is fit onto the cooled surfaces 300A, 300B of the dual-side cooled power module 100. A heat receiving spacer 300A is comprised of a heat receiving part 301A which has a substantially rectangular plate form and a pair of hollow space providing sections 302A which have a substantially cuboidal form, protruding toward a heat receiving spacer 300B from both edges of the heat receiving part 301A. In the heat receiving part 301A, a great number of columnar through holes 303A (concave portions) are formed. These through holes 303A are formed in positions facing the pin fins 122A of the cooled surface 121A and have a diameter that is slightly larger than the diameter of a pin fin 122A. Like the heat receiving spacer 300A, the heat receiving spacer 300B is also comprised, of a heat receiving part 301B which has a substantially rectangular plate form and a pair of hollow space providing sections 302B which have a substantially cuboidal form, protruding toward the heat receiving spacer 300B from both edges of the heat receiving part 301B. The heat receiving spacer 300B has a shape that is upside down symmetrical with respect to the heat receiving spacer 300A, but, in the heat receiving part 301B, through holes 303B are formed in positions facing the respective pin fins 122B protruding from the cooled surface 121B of the dual-side cooled power module 100.

When attaching the heat receiving spacers 300A, 300B to the dual-side cooled power module 100, apply heat conductive grease over the cooled surfaces 121A, 121B and put the hollow space providing sections 302A, 302B abutting against each other, while positioning the through holes 303A, 303B in alignment with the respective pin fins 122. A state in which heat receiving spacers 300A, 300B are attached to the dual-side cooled power module 100 in this way is depicted in FIG. 8. As depicted, the cooled surfaces 121A, 121B of the main body part 101 are mostly covered by the heat receiving spacers 300A, 300B, though a side end face 101 a of the main body part is exposed.

FIG. 9 is a cross-sectional view through line A-A′ in FIG. 8. When the hollow space providing sections 302A, 302B are put abutting against each other, the surfaces, facing a heat generator, of the heat receiving parts 301A, 301B face with each other with an interval as long as a distance d2 between them. That is, the heat receiving spacers 300A, 300B are formed so that the distance d2 is slightly longer than the thickness d1 of the main body part 101 of the dual-side cooled power module 100. In consequence, gaps 310A, 310B are formed between the heat receiving part 301A and the main body part 101 and between the heat receiving part 301B and the main body part 101, respectively. The gaps 310A, 310B do not necessarily have an equal width, since the dual-side cooled power module 100 has play with respect to the heat receiving spacers 300A, 300B.

When the hollow space providing sections 302A, 302B are put abutting against each other, heat conductive grease (not depicted) applied over the pin fins is pushed to enter the gaps 310A, 310B and the gaps 310A, 310B are also filled with heat conductive grease without space. Given that d4 denotes the thickness of the main body part 101 from the tips of the pin fins 122A to the tips of the pin fins 122B and d5 denotes the entire width when the heat receiving spacers 300A, 300B are put abutting against each other, the heat receiving spacers 300A, 300B are formed so that the width d5 will be slightly wider than the thickness d4. Thereby, gaps 311A, 311B are formed between the upper surface of the heat receiving spacer 300A and the tips of the pin fins 122A and between the lower surface of the heat receiving spacer 300B and the tips of the pin fins 122B in the drawing, respectively. The gaps 311A, 311B do not necessarily have an equal width, since the dual-side cooled power module 100 has play with respect to the heat receiving spacers 300A, 300B as described previously.

When the heat receiving spacers 300A, 300B are attached to a cooler 400 (which will be detailed later) pressing force 320 is applied, as indicated by hatched arrows. This pressing force 320 is applied to portions where hollow space providing sections 302A, 302B abut against each other. That is, this pressing force 320 is not applied to the main body part 101, since the gaps 310A, 310B are formed between the main body part 101 and the heat receiving spacers 300A, 300B and the gaps 311A, 311B are formed in the portions adjacent to the tips of the pin fins 122A, 122B, these gaps being made by the hollow space providing sections 302A and 302B.

FIG. 10 is a perspective view depicting a state in which two dual-side cooled power modules 100 are attached to the cooler 400. The cooler 400 is comprised of a pair of coolers 400A, 400B. The coolers 400A, 400B have clamping members 410A, 410B formed in a substantially cuboidal block, respectively. Two dual-side cooled power modules 100, to each of which the heat receiving spacers 300A, 300B are attached, are sandwiched between and clamped by these clamping members 410A, 410B.

The clamping members 410A, 410B are mutually tightened with a plurality of fasteners 420 and pressing force 320 is applied to the clamping members 410A, 410B in a direction indicated by hatched arrows. However, as described for FIG. 9, this force 320 is applied to the heat receiving spacers 300A, 300B, but is not applied to the dual-side cooled power modules 100. As the fasteners 420, bolts and nuts which are commonly used can be used.

In FIG. 10, four heat pipes 430 protrude from the clamping member 410A, slanting at an angle of about 10° with respect to an x-y plane (horizontal plane) formed by x and y axes. A plurality of plate-like heat radiation fins 440 is welded to these heat pipes 430 in their radial direction. Therefore, each heat radiation fin 440 slants at an angle of about 10° with respect to an x-z plane (vertical plane) formed by x and z axes. A cooler 400B is configured in the same way as for the cooler 400A. By thus mounting two dual-side cooled power modules 100 to the cooler 400, an air-cooled dual-side cooled power unit 500 is configured.

When the dual-side cooled power modules 100 generate heat, the heat is transferred via the heat receiving spacers 300A, 300B to the clamping members 410A, 410B and further transferred backward (in the y-axis direction) through the heat pipes 430. When cooling wind 441 directed from bottom to top (directed in the z-axis direction) is blown into this air-cooled dual-side cooled power unit 500, the cooling wind 441 moves upward, while cooling the heat radiation fins 440 and, thus, the heat is expelled rapidly. Paths of such heat transfer are indicated by arrows 431 in the drawing. Heat transfer in a direction perpendicular to the direction of the cooling wind 441 is mainly due to the heat pipes 430.

FIG. 11 is an exploded view of region B surrounded by dashed lines presented in FIG. 10. In FIG. 11, heat conductive grease 450 is applied between the heat receiving spacer 300A and the clamping member 410A and between the heat receiving spacer 300B and the clamping member 410B, respectively. When the clamping members 410A, 410B are tightened with the fasteners 420, the heat conductive grease 450 spreads over an interface plane between the heat receiving spacer 300A and the clamping member 410A and an interface plane between the heat receiving spacer 300B and the clamping member 410B and makes thin film layers as depicted. At the same time, the heat conductive grease 450 also enters the gaps 311A, 311B in the portions adjacent to the tips of the pin fins 122A, 122B (see FIG. 9) and the outsides of the pin fins 122A, 122B are immersed in the heat conductive grease 450.

FIG. 12 is a cross-sectional view through line C-C′ in FIG. 11. Placing the clamping member 410A on the upper surface of the heat receiving spacer 300A provides a thermal connection surface at the interface between both. To transfer heat of the dual-side cooled power module 100 to the claiming member 410A efficiently, the tips of the pin fins 122A and the heat receiving part 301A of the heat receiving spacer 300A must connect with the clamping member 410A in a smooth condition.

FIG. 13 is an enlarged view of portion D presented in FIG. 12. In the present embodiment, a region (which is hatched in FIG. 13) that is formed by the cooled surface 121A, pins fins 122A, heat receiving part 301A, and clamping member 410A is filled with heat conductive grease 450. At this time, heat of the dual-side cooled power module 100 is transferred to the clamping member 410A through heat dissipation paths 130, 131, 132 indicate by dashed lines. A heat dissipation path 130 is a path through which heat is transferred from the main body part 101 via the heat receiving part 301A to the clamping member 410A. A heat dissipation path 131 is a path through which heat is conducted from the main body part 101 to the pin fin 122A and transferred via the heat conductive grease 450 to the clamping member 410A. A heat dissipation path 132 is a path through which heat migrates from the pin fin 122A to the heat receiving part 301A and then the heat is transferred to the clamping member 410A. The present embodiment enables dissipating heat of the dual-side cooled power module 100 through making effective use of the entire outer surfaces of the pin fins 122A. As described above, it is enabled to dissipate heat through a plurality of paths via heat conductive grease in the present embodiment, and, therefore, heat can be dissipated efficiently.

When viewing the power module 100 which is a heat generator from a direction parallel to a direction in which the convex portions formed on the power module protrude (that is, when viewing the power module 100 from −X axis direction toward +X axis direction in FIG. 13), a filler area where the heat conductive material is filled between the heat receiving spacer 300A and the clamping member 410A is larger than a filler area where the heat conductive material is filled between the through hole 303A and the pin fin 122A and between the cooled surface 121A and the heat receiving part 301A. When heat is transferred from the heat receiving spacer 300A to the clamping member 410A, heat will spread inside the heat receiving spacer 300A; therefore, the filler area between the heat receiving spacer 300A and the clamping member 410A is enlarged for transferring heat more efficiently. This configuration makes it possible to dissipate heat more effectively, when heat diffuses from the heat generator via the pin fins 122A and the heat receiving spacer 300A. The same configuration can be adopted also in second and third embodiments which will be described later and the same advantageous effect can be obtained.

Moreover, if the main body part 101 has swollen by thermal deformation of the dual-side cooled power module 100, swelling stress is released by fluid deformation of the heat conductive grease 450. At this time, because the gap 315 between the tips of the pin fins 122A and the clamping member 410A is larger than the gap 311A between the upper surface of the heat receiving spacer 300A and the tips of the pin fins 122A, the tips of the pins fins 122A do not abut against the clamping member 410A and a good thermal connection condition is maintained. The side of the clamping member 410B is configured in the same way as for the side of the clamping member 410A.

Second Embodiment

FIG. 14 depicts a second embodiment of the present invention, in which thermal connections in the first embodiment are provided by heat conductive sheets 451.

FIG. 15 is an enlarged view of portion E in FIG. 14. The heat receiving part 301A of the heat receiving spacer 300A and the clamping member 410A as well as the heat receiving part 301A and the cooled surface 121A of the dual-side cooled power module 100 are thermally connected by heat conductive sheets 451 which are of sheet form. Commonly used heat conductive sheets 451 have a lower fluidity than heat conductive grease 450, but their heat conduction performance is high. Therefore, even though it is impossible to connect each pin fin 122A and the heat receiving part 301A by a heat conductive sheet 451, heat dissipation performance is compensated by heat transfer through heat dissipation paths 130, 131. Although two heat conductive sheets 151 are layered over the tips of the pin fins 122A in FIG. 15, this layer may be configured with one sheet, making effective use of the deformability of a heat conductive sheet 451 in its thickness direction.

Third Embodiment

FIG. 16 depicts a third embodiment of the present invention, in which the power semiconductor module of the first embodiment is configured as a one side cooled power module 600. The one side cooled power module 600 is comprised of an element mount part 651 in which elements are installed and a base 652 in which an insulation substrate providing electrical insulation is installed. The element mount part 651 and the base 652 are bonded by brazing, for example.

FIG. 17 is an enlarged view of portion F in FIG. 16. In the present configuration, there are thermal connections between a heat receiving part 611 of a heat receiving spacer 610 and the base 652, between a through hole 612 of the heat receiving spacer 610 and a pin fin 653 of the base 610, and between the heat receiving part 611 and a clamping member 410. In the present embodiment, gaps are filled with heat conductive grease 450 to provide the thermal connections, enabling heat dissipation making effective use of the entire outer surfaces of the pin fins 653. Therefore, it is possible to transfer heat from the heat generator efficiently. 

1. A structure for cooling a heat generator comprising: a heat generator having at least one cooled surface having protruding convex portions formed thereon; a heat receiving spacer in which hollow portions into which the convex portions are inserted are formed; clamping members which press and clamp the heat receiving spacer and the heat generator sandwiched therebetween; and a cooler which cools the heat receiving spacer, wherein, in an engagement state in which the heat generator and the heat receiving spacer are engaged by the clamping members, a distance between the cooled surface and the end faces of the convex portions is smaller than a distance between the cooled surface and a face, facing either of the clamping members, of the heat receiving spacer.
 2. The structure for cooling a heat generator according to claim 1, wherein, in an engagement state in which the convex portions of the heat generator have been engaged in the hollow portions of the heat receiving spacer, gaps formed between the convex portions and the hollow portions are filled with a first heat conductive material.
 3. The structure for cooling a heat generator according to claim 1, wherein gaps formed between one of the clamping members and a face, facing the one of the clamping members, of the heat receiving spacer are filled with a second heat conductive material.
 4. The structure for cooling a heat generator according to claim 3, wherein, when viewing the heat generator from a direction parallel to a direction in which the convex portions protrude, a filler area where the second heat conductive material is filled is larger than a filler area where the first heat conductive material is filled.
 5. The structure for cooling a heat generator according to claim 1, wherein the hollow portions are through holes.
 6. The structure for cooling a heat generator according to claim 2, wherein the heat conductive material is heat conductive grease.
 7. The structure for cooling a heat generator according to claim 1, wherein the clamping members clamp a pair of heat receiving spacers, each facing either of dual opposite sides of the heat generator, sandwiched therebetween and cools the heat generator by contacting heat pipes, and wherein the heat pipes are provided with heat radiation fins.
 8. Power conversion equipment comprising: a heat generator having at least one cooled surface having protruding convex portions formed thereon; a heat receiving spacer in which hollow portions into which the convex portions are inserted are formed; clamping members which press and clamp the heat receiving spacer and the heat generator sandwiched therebetween; a cooler which cools the heat receiving spacer; heat pipes brought in contact with the camping members; and heat radiation fins provided on the heat pipes, wherein, in an engagement state in which the heat generator and the heat receiving spacer are engaged by the clamping members, a distance between the cooled surface and the end faces of the convex portions is smaller than a distance between the cooled surface and a face, facing either of the clamping members, of the heat receiving spacer. 